(1) Field of the Invention
The present invention relates to a method for improving the light-resistance of aromatic polyamide fibers. More particularly, it relates to a method for improving the light-resistance of aromatic polyamide fibers useful in the textile field where a high light-resistance is required.
(2) Description of the Prior Art
It is known that aromatic polyamides are advantageously used in various fields. Aromatic polyamides have higher softening and melting points than those of aliphatic polyamides such as nylon-6 and nylon-6.6 and are excellent in heat-resistance characteristics such as the strength retention ratio and dimensional stability at high temperatures and the resistance to thermal decomposition, flame retardance, fire retardance, the chemical resistance, electric characteristics, and mechanical properties such as the tenacity and Young's modulus. Since aromatic polyamides have very desirable physical and chemical properties as mentioned above, they are especially suitably used for the production of heat-resistant fibers, flame-retardant fibers and fire-proofing fibers and high-tenacity, high-Young's modulus fibers and films. For example, aromatic polyamides are widely used as electrically insulating materials for motors or transformers, as industrial materials for production of filter bags and heating pipes and as textile materials for woven fabrics for which an aesthetic effect is not particularly required. In the field of textile fibers where fashionable colors are considered important, aromatic polyamides are used for heat-resistant safety clothes such as aircraft jackets and fire jackets. Moreover, blended yarns and mixed woven and knitted fabrics of aromatic polyamide fibers with rayon, cotton or wool, exhibit sweat-absorbing, moisture-absorbing and heat-insulating properties in addition to the above-mentioned excellent characteristics of aromatic polyamides, and are now used for sports wears and comfortable wears that can be worn under a heavy duty. With recent increase of utilization of aromatic polyamides in the textile field, the problem of a poor light-resistance of poor light fastness has become serious.
As means for improving the light-resistance of aromatic polyamide fibers, there has been disclosed a method in which an ultraviolet absorbent is incorporated at the dyeing step. However, since aromatic polyamide fibers are essentially difficult to dye, the dispersion of the ultraviolet absorbent within the fibers is low, and no satisfactory results can be obtained according to this method. Moreover, even if a carrier is used as an absorption promoter, the ultraviolet absorbent is not sufficiently introduced into the fibers, and hence, no substantial effect of improving the light-resistance can be obtained.